Today I tried to do a short course. Before hitting the start button (see screenshot below), I drove the pedals a few times and then stopped pedaling. The power and cadence immediately went to zero as well (when the brake roller also stopped), but the speed still showed high values. The speed only dropped very slowly (for example after 10 seconds standing still, it still showed 13.8 km/h). Is this a known issue? The speed should show 0 km/h as soon as the brake roller stops, right?

This was on a Genius Smart.

Last edited by Loek on Fri Dec 29, 2017 8:21 pm, edited 1 time in total.

Between the img tags there must be a URL of the picture that you can find by clicking on it with the right mouse button or by reading the html code of the page where the picture is located. For example:

No, I'm not using any other sensors, just the Genius itself. I'll test with the Utility app. Do you know of more Android apps where I can test with?

Okay, I just tested with the 'Utility' app that shows the speed as well. In this app, the speed drops to zero as soon as the brake roller stops spinning. So the Utility app shows it correctly. Seems that it's the Android Training App which has the bug then. How should I report this to Tacx? Is posting this topic enough, or should I do more?

The values of these parameters outside the training frame (before and after the end) can indeed have such oddities.

I did some further testing. But not only before and after the end the speed is wrong; also during the activity, the speed shows non-zero values while standing still. See the screenshots below, during the activity. You can see that the power and cadence values show zero (correct), but for those periods of time the speed is non-zero and only slowly decreasing.

When looking at the activity on Tacx Cloud, also the speed is shown incorrectly, see the screenshot below. So it seems that not only the visualization in the mobile app is wrong, but also the actual logging (hence Tacx Cloud also shows the wrong values when reviewing the activity). Hopefully this bug can be fixed soon.

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Another example where the speed is wrong: this time when doing a .gpx ride on the mobile app.

The app no longer reports the speed measured in the break itself, but also takes into account your weight, air resistance and, most relevant in this case, slope. Based on all these values the speed you would have while cycling on the road is simulated. In this case, you're heading down a .5% slope. Like in real life, if you'd stop pedaling, this means you will not stop immediately, as you're still "going down hill". I see a lot of confusion related to virtual speed and we should figure out how to explain it a bit better (as we don't really do so now) but the math is actually correct. We did test/calculate it multiple times and it does match what is expected, when considering proper physics.

Hi Gijs, thanks for responding here. I did some further tests. And it indeed seems that the higher the percentage, the faster the speed goes to zero once stopping pedaling. So this part makes sense.

However, it does so very unrealistically. For example, on a 7% hill, it takes about 17(!) seconds before the speed is zero after stopping pedaling when going only 10 km/h. In reality, this would only take like 4 or 5 seconds at most I think. For a 1% slope it takes 23 seconds, and for an 11% slope, it takes 15(!) seconds according to the Android app. This is completely unrealistic, isn't it? The brake was calibrated and in the center (green) area.

When reviewing the activity on Tacx Cloud, the analysis graph shows different values for some reason. There, the time it takes to reach zero speed is much shorter, but still too long. For example, instead of 15s for an 11% hill, it still takes 8 seconds. It's lower, but still way too long.

So two issues still present it seems:

1. Mainly the Android app (but also on Tacx Cloud), the speed drops to zero too slowly, and is not realistic.
2. The values as shown 'live' on the Android app do not match with the analysis graph in Tacx Cloud.

If you need some further data (screen recordings/video), let me know what you need and I'll try to provide.

I checked with some basic maths and physics (only taking into account gravitational force), and if I did the calculations right, it would only take about 2.6 seconds before one would come to a standstill after stopping pedaling from 10 km/h on an 11% slope. That's a lot shorter than 15 seconds... I was not even taking into account rolling resistance and air resistance, which would make the 2.6 seconds even shorter.

We did test/calculate it multiple times and it does match what is expected, when considering proper physics.

Not sure what physics you are using, but it might be good to have one more check . Hopefully the issue can be solved so we have more realistic numbers. If you need more details on my calculations, let me know.